Lubricant compositions for direct injection engines

ABSTRACT

The invention is directed to a method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine by supplying to the sump a lubricant composition which contains an oil of lubricating viscosity and a metal overbased detergent. The metal overbased detergent may be selected from sulfonate detergents, phenate detergents, and salicylate detergents, especially sulfonate detergents with a metal ratio of at least 5.

BACKGROUND OF THE INVENTION

The disclosed technology relates to lubricants for internal combustionengines, particularly those for spark-ignited direct injection engines.

Modern engine designs are being developed to improve fuel economywithout sacrificing performance or durability. Historically, gasolinewas port-fuel injected (PFI), that is, injected through the air intakeand entering the combustion chamber via the air intake valve. Gasolinedirect injection (GDI) involves direct injection of gasoline into thecombustion chamber.

In certain situations, the internal combustion engine may exhibitabnormal combustion. Abnormal combustion in a spark-initiated internalcombustion engine may be understood as an uncontrolled explosionoccurring in the combustion chamber as a result of ignition ofcombustible elements therein by a source other than the igniter.

Pre-ignition may be understood as an abnormal form of combustionresulting from ignition of the air-fuel mixture prior to ignition by theigniter. Anytime the air-fuel mixture in the combustion chamber isignited prior to ignition by the igniter, such may be understood aspre-ignition. It will also be understood that ignition events generallyincrease in likelihood as the air-fuel ratio becomes leaner. As such,one approach to preventing pre-ignition events in GDI engines has beento intentionally inject additional fuel (i.e., to overfuel), therebyadjusting the air-fuel ratio to a richer mixture that is less favorableto pre-ignition events. This approach has successfully treated LSPI, butmore current fuel efficiency and economy standards are causing enginemanufacturers to adopt leaner air-fuel mixtures, which leads to the needfor alternative approaches to preventing or reducing LSPI events.

Without being bound to a particular theory, traditionally, pre-ignitionhas occurred during high speed operation of an engine when a particularpoint within the combustion chamber of a cylinder may become hot enoughduring high speed operation of the engine to effectively function as aglow plug (e.g. overheated spark plug tip, overheated burr of metal) toprovide a source of ignition which causes the air-fuel mixture to ignitebefore ignition by the igniter. Such pre-ignition may be more commonlyreferred to as hot-spot pre-ignition, and may be inhibited by simplylocating the hot spot and eliminating it.

More recently, vehicle manufacturers have observed intermittent abnormalcombustion in their production of turbocharged gasoline engines,particularly at low speeds and medium-to-high loads. More particularly,when operating the engine at speeds less than or equal to 3,000 rpm andunder a load with a brake mean effective pressure (BMEP) of greater thanor equal to 10 bars, a condition which may be referred to as low-speedpre-ignition (LSPI) may occur in a very random and stochastic fashion.

The disclosed technology provides a method for reducing, inhibiting, oreven eliminating LSPI events in direct injection engines by operatingthe engines with a lubricant that contains a metal overbased detergent.

SUMMARY OF THE INVENTION

The disclosed technology provides a method for reducing low speedpre-ignition events in a spark-ignited direct injection internalcombustion engine comprising supplying to the sump a lubricantcomposition which contains an oil of lubricating viscosity and a metaloverbased detergent. The metal overbased detergent may be selected fromsulfonate detergents, phenate detergents, and salicylate detergents,especially sulfonate detergents.

The invention provides method for reducing low speed pre-ignition eventsin a spark-ignited direct injection internal combustion enginecomprising supplying to the engine a lubricant composition comprising abase oil of lubricating viscosity and a metal overbased detergent.

The invention further provides the method described herein in which theengine is operated under a load with a brake mean effective pressure(BMEP) of greater than or equal to 10 bars.

The invention further provides the method described herein in which theengine is operated at speeds less than or equal to 3,000 rpm.

The invention further provides the method described herein in which theengine is fueled with a liquid hydrocarbon fuel, a liquid nonhydrocarbonfuel, or mixtures thereof.

The invention further provides the method described herein in which theengine is fueled by natural gas, liquefied petroleum gas (LPG),compressed natural gas (CNG), or mixtures thereof.

The invention further provides the method described herein in which themetal overbased detergent includes one or more of a sulfonate detergent,a phenate detergent, a salicylate detergent, and combinations thereof.

The invention further provides the method described herein in which thelubricant composition further includes at least one other additiveselected from an ashless dispersant, an ashless antioxidant, aphosphorus-containing anti-wear additive, a friction modifier, and apolymeric viscosity modifier.

The invention further provides the method described herein in which themetal overbased detergent comprises a sulfonate detergent.

The invention further provides the method described herein in which themetal overbased detergent comprises a salicylate detergent.

The invention further provides the method described herein in which themetal overbased detergent comprises an alkali metal or an alkaline earthmetal detergent.

The invention further provides the method described herein in which themetal overbased detergent has a metal ratio of 5 to 30.

The invention further provides the method described herein in which themetal overbased detergent is present in an amount from 0.2 to 8 weightpercent of the lubricant composition.

The invention further provides the method described herein in which thelubricating composition further includes a polyalkenyl succinimidedispersant in an amount from 0.5 to 4 weight % of the composition.

The invention further provides the method described herein in which thelubricating composition includes at least 50 weight % of a Group II baseoil, a Group III base oil, or mixtures thereof.

The invention further provides the method described herein in which themetal overbased detergent comprises a sulfur-coupled phenate detergent.

The invention further provides the method described herein in which themetal overbased detergent is present in an amount to provide 0.1 weightpercent to 0.9 weight percent sulfated ash to the lubricatingcomposition.

The invention further provides the method described herein in whichthere is a reduction in the number of LSPI events of at least 10percent.

The invention further provides the method described herein in which thelow speed pre-ignition events are reduced to less than 20 LSPI eventsper 100,000 combustion events.

DETAILED DESCRIPTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

As indicated above, when operating the engine at speeds less than orequal to 3,000 rpm and under a load with a brake mean effective pressure(BMEP) of greater than or equal to 10 bars, a low-speed pre-ignition(LSPI) event may occur in the engine. A LSPI event may consist of one ormore LSPI combustion cycles, and generally consists of multiple LSPIcombustion cycles which occur in a consecutive fashion or alternatingfashion with normal combustion cycles in between. Without being bound toa particular theory, LSPI may result from a combustion of oildroplet(s), or a droplet(s) of oil-fuel mixture, or combinationsthereof, which may accumulate, for example, in the top land crevicesvolume of a piston, or the piston ring-land and ring-groove crevices.The lubricant oil may be transferred from below the oil control ring tothe piston top land area due to unusual piston ring movements. At lowspeed, high load conditions, in-cylinder pressures dynamics (compressionand firing pressures) may be considerably different from in-cylinderpressures at lower loads, particularly due to strongly retardedcombustion phasing and high boost and peak compression pressures whichcan influence ring motion dynamics.

At the foregoing loads, LSPI, which may be accompanied by subsequentdetonation and/or severe engine knock, can cause severe damage to theengine very quickly (often within 1 to 5 engine cycles). Engine knockmay occur with LSPI given that, after the normal spark from the igniteris provided, multiple flames may be present. The present invention aimsto provide a method for inhibiting or reducing LSPI events, the methodinvolving supplying to the engine a lubricant comprising a metaloverbased detergent.

In one embodiment of the invention, the engine is operated at speedsbetween 500 rpm and 3000 rpm, or 800 rpm to 2800 rpm, or even 1000 rpmto 2600 rpm. Additionally, the engine may be operated with a brake meaneffective pressure of 10 bars to 30 bars, or 12 bars to 24 bars.

LSPI events, while comparatively uncommon, may be catastrophic innature. Hence drastic reduction or even elimination of LSPI eventsduring normal or sustained operation of a direct fuel injection engineis desirable. In one embodiment, the method of the invention is suchthat there are less than 20 LSPI events per 100,000 combustion events orless than 10 LSPI events per 100.000 combustion events. In oneembodiment, there may be less than 5 LSPI events per 100.000 combustionevents, less than 3 LSPI events per 100.000 combustion events; or theremay be 0 LSPI events per 100.000 combustion events.

In one embodiment, the method of the invention provides a reduction inthe number of LSPI events of at least 10 percent, or at least 20percent, or at least 30 percent, or at least 50 percent.

Fuel

The method of the present invention involves operating a spark-ignitedinternal combustion engine. In addition to the engine operatingconditions and the lubricant composition, the composition of the fuelmay impact LSPI events. In one embodiment, the fuel may comprise a fuelwhich is liquid at ambient temperature and is useful in fueling a sparkignited engine, a fuel which is gaseous at ambient temperatures, orcombinations thereof.

The liquid fuel is normally a liquid at ambient conditions e.g., roomtemperature (20 to 30° C.). The fuel can be a hydrocarbon fuel, anonhydrocarbon fuel, or a mixture thereof. The hydrocarbon fuel may be agasoline as defined by ASTM specification D4814. In an embodiment of theinvention the fuel is a gasoline, and in other embodiments the fuel is aleaded gasoline, or a nonleaded gasoline.

The nonhydrocarbon fuel can be an oxygen containing composition, oftenreferred to as an oxygenate, to include an alcohol, an ether, a ketone,an ester of a carboxylic acid, a nitroalkane, or a mixture thereof. Thenonhydrocarbon fuel can include for example methanol, ethanol, methylt-butyl ether, methyl ethyl ketone, transesterified oils and/or fatsfrom plants and animals such as rapeseed methyl ester and soybean methylester, and nitromethane. Mixtures of hydrocarbon and nonhydrocarbonfuels can include, for example, gasoline and methanol and/or ethanol. Inan embodiment of the invention, the liquid fuel is a mixture of gasolineand ethanol, wherein the ethanol content is at least 5 volume percent ofthe fuel composition, or at least 10 volume percent of the composition,or at least 15 volume percent, or 15 to 85 volume percent of thecomposition. In one embodiment, the liquid fuel contains less than 15%by volume ethanol content, less than 10% by volume ethanol content, lessthan 5% ethanol content by volume, or is substantially free of (i.e.less than 0.5% by volume) of ethanol.

In several embodiments of this invention, the fuel can have a sulfurcontent on a weight basis that is 5000 ppm or less, 1000 ppm or less,300 ppm or less, 200 ppm or less, 30 ppm or less, or 10 ppm or less. Inanother embodiment, the fuel can have a sulfur content on a weight basisof 1 to 100 ppm. In one embodiment, the fuel contains about 0 ppm toabout 1000 ppm, about 0 to about 500 ppm, about 0 to about 100 ppm,about 0 to about 50 ppm, about 0 to about 25 ppm, about 0 to about 10ppm, or about 0 to 5 ppm of alkali metals, alkaline earth metals,transition metals or mixtures thereof. In another embodiment the fuelcontains 1 to 10 ppm by weight of alkali metals, alkaline earth metals,transition metals or mixtures thereof.

The gaseous fuel is normally a gas at ambient conditions e.g., roomtemperature (20 to 30° C.). Suitable gas fuels include natural gas,liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixturesthereof. In one embodiment, the engine is fueled with natural gas.

The fuel compositions of the present invention can further comprise oneor more performance additives. Performance additives can be added to afuel composition depending on several factors, including the type ofinternal combustion engine and the type of fuel being used in thatengine, the quality of the fuel, and the service conditions under whichthe engine is being operated. In some embodiments, the performanceadditives added are free of nitrogen. In other embodiments, theadditional performance additives may contain nitrogen.

The performance additives can include an antioxidant such as a hinderedphenol or derivative thereof and/or a diarylamine or derivative thereof;a corrosion inhibitor such as an alkenylsuccinic acid; and/or adetergent/dispersant additive, such as a polyetheramine or nitrogencontaining detergent, including but not limited to polyisobutylene (PIB)amine dispersants, Mannich detergents, succinimide dispersants, andtheir respective quaternary ammonium salts.

The performance additives may also include a cold flow improver, such asan esterified copolymer of maleic anhydride and styrene and/or acopolymer of ethylene and vinyl acetate; a foam inhibitor, such as asilicone fluid; a demulsifier such as a polyoxyalkylene and/or an alkylpolyether alcohol; a lubricity agent such as a fatty carboxylic acid,ester and/or amide derivatives of fatty carboxylic acids, or esterand/or amide derivatives of hydrocarbyl substituted succinic anhydrides;a metal deactivator, such as an aromatic triazole or derivative thereof,including but not limited to a benzotriazole such as tolytriazole;and/or a valve seat recession additive, such as an alkali metalsulfosuccinate salt. The additives may also include a biocide, anantistatic agent, a deicer, a fluidizer, such as a mineral oil and/or apoly(alpha-olefin) and/or a polyether, and a combustion improver, suchas an octane or cetane improver.

The fluidizer may be a polyetheramine or a polyether compound. Thepolyetheramine can be represented by the formula R[—OCH₂CH(R¹)]_(n)A,where R is a hydrocarbyl group, R¹ is selected from the group consistingof hydrogen, hydrocarbyl groups of 1 to 16 carbon atoms, and mixturesthereof, n is a number from 2 to about 50, and A is selected from thegroup consisting of —OCH₂CH₂CH₂NR²R² and —NR³R³, where each R² isindependently hydrogen or hydrocarbyl, and each R³ is independentlyhydrogen, hydrocarbyl or —[R⁴N(R⁵)]_(p)R⁶, where R⁴ is C₂-C₁₀ alkylene,R⁵ and R⁶ are independently hydrogen or hydrocarbyl, and p is a numberfrom 1-7.

The fluidizer can be a polyether, which can be represented by theformula R⁷O[CH₂CH(R⁸)O]_(q)H, where R⁷ is a hydrocarbyl group, R⁸ isselected from the group consisting of hydrogen, hydrocarbyl groups of 1to 16 carbon atoms, and mixtures thereof, and q is a number from 2 toabout 50. The fluidizer can be a hydrocarbyl-terminatedpoly(oxyalkylene) aminocarbamate as described U.S. Pat. No. 5,503,644.The fluidizer can be an alkoxylate, wherein the alkoxylate can comprise:(i) a polyether containing two or more ester terminal groups; (ii) apolyether containing one or more ester groups and one or more terminalether groups; or (iii) a polyether containing one or more ester groupsand one or more terminal amino groups, wherein a terminal group isdefined as a group located within five connecting carbon or oxygen atomsfrom the end of the polymer. Connecting is defined as the sum of theconnecting carbon and oxygen atoms in the polymer or end group.

The performance additives which may be present in the fuel additivecompositions and fuel compositions of the present invention also includedi-ester, di-amide, ester-amide, and ester-imide friction modifiersprepared by reacting a dicarboxylic acid (such as tartaric acid) and/ora tricarboxylic acid (such as citric acid), with an amine and/oralcohol, optionally in the presence of a known esterification catalyst.These friction modifiers often derived from tartaric acid, citric acid,or derivatives thereof, may be derived from amines and/or alcohols thatare branched so that the friction modifier itself has significantamounts of branched hydrocarbyl groups present within it structure.Examples of suitable branched alcohols used to prepare these frictionmodifiers include 2-ethylhexanol, isotridecanol, Guerbet alcohols, ormixtures thereof.

In different embodiments the fuel composition may have a composition asdescribed in the following table:

Embodiments (ppm) Additive A C D Detergent/dispersant 0 to 2500 25 to150 500 to 2500 Fluidizer 0 to 5000  1 to 250 3000 to 5000  Demulsifier0 to 50 0.5 to 5   1 to 25 Corrosion Inhibitor 0 to 200 .5 to 10  20 to200 Antioxidant 0 to 1000  5 to 125 500 to 1000 Friction Modifier 0 to600 50 to 175 100 to 750  Fuel Balance to Balance to 100% Balance to100% 100%Oil of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity.Such oils include natural and synthetic oils, oil derived fromhydrocracking, hydrogenation, and hydrofinishing, unrefined, refined,re-refined oils or mixtures thereof. A more detailed description ofunrefined, refined and re-refined oils is provided in InternationalPublication WO2008/147704, paragraphs [0054] to [0056] (a similardisclosure is provided in US Patent Publication 2010/0197536, see [0072]to [0073]). A more detailed description of natural and syntheticlubricating oils is described in paragraphs [0058] to [0059]respectively of WO2008/147704 (a similar disclosure is provided in USPatent Publication 2010/0197536, see [0075] to [0076]). Synthetic oilsmay also be produced by Fischer-Tropsch reactions and typically may behydroisomerised Fischer-Tropsch hydrocarbons or waxes. In oneembodiment, oils may be prepared by a Fischer-Tropsch gas-to-liquidsynthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in theApril 2008 version of “Appendix E—API Base Oil InterchangeabilityGuidelines for Passenger Car Motor Oils and Diesel Engine Oils”, section1.3 Sub-heading 1.3. “Base Stock Categories”. The API Guidelines arealso summarized in U.S. Pat. No. 7,285,516 (see column 11, line 64 tocolumn 12, line 10). In one embodiment, the oil of lubricating viscositymay be an API Group II, Group III, or Group IV oil, or mixtures thereof.The five base oil groups are as follows:

Base Oil Category Sulfur (%) Saturates (%) Viscosity Index Group I >0.03 and/or <90 80 to 120 Group II ≤0.03 and ≥90 80 to 120 Group III≤0.03 and ≥90 ≥120 Group IV All polyalphaolefins (PAO) Group V Allothers not included in Groups I, II, III, or IV

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 weight % (wt %) the sum ofthe amount of the compound of the invention and the other performanceadditives.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention (comprising the additives disclosed herein) is in the form ofa concentrate which may be combined with additional oil to form, inwhole or in part, a finished lubricant), the ratio of the of theseadditives to the oil of lubricating viscosity and/or to diluent oilinclude the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 byweight.

In one embodiment, the base oil has a kinematic viscosity at 100° C.from 2 mm²/s (centiStokes—cSt) to 16 mm²/s, from 3 mm²/s to 10 mm²/s, oreven from 4 mm²/s to 8 mm²/s.

The ability of a base oil to act as a solvent (i.e. solvency) may be acontributing factor in increasing the frequency of LSPI events duringoperation of a direct fuel-injected engine. Base oil solvency may bemeasured as the ability of an un-additized base oil to act as a solventfor polar constituents. In general, base oil solvency decreases as thebase oil group moves from Group I to Group IV (PAO). That is, solvencyof base oil may be ranked as follows for oil of a given kinematicviscosity: Group I>Group II>Group III>Group IV. Base oil solvency alsodecreases as the viscosity increases within a base oil group; base oilof low viscosity tends to have better solvency than similar base oil ofhigher viscosity. Base oil solvency may be measured by aniline point(ASTM D611).

In one embodiment, the base oil comprises at least 30 wt % of Group IIor Group III base oil. In another embodiment, the base oil comprises atleast 60 weight % of Group II or Group III base oil, or at least 80 wt %of Group II or Group III base oil. In one embodiment, the lubricantcomposition comprises less than 20 wt % of Group IV (i.e.polyalphaolefin) base oil. In another embodiment, the base oil comprisesless than 10 wt % of Group IV base oil. In one embodiment, thelubricating composition is substantially free of (i.e. contains lessthan 0.5 wt %) of Group IV base oil.

Ester base fluids, which are characterized as Group V oils, have highlevels of solvency as a result of their polar nature. Addition of lowlevels (typically less than 10 wt %) of ester to a lubricatingcomposition may significantly increase the resulting solvency of thebase oil mixture. Esters may be broadly grouped into two categories:synthetic and natural. An ester base fluid would have a kinematicviscosity at 100° C. suitable for use in an engine oil lubricant, suchas between 2 cSt and 30 cSt, or from 3 cSt to 20 cSt, or even from 4 cStto 12 cSt.

Synthetic esters may comprise esters of dicarboxylic acids (e.g.,phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinicacids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaricacid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonicacids, and alkenyl malonic acids) with any of variety of monohydricalcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol,2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, andpropylene glycol). Specific examples of these esters include dibutyladipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinoleic acid dimer, and the complex ester formed by reacting one moleof sebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid. Other synthetic esters include those made from C5to C12 monocarboxylic acids and polyols and polyol ethers such asneopentyl glycol, trimethylolpropane, pentaerythritol,dipentaerythritol, and tripentaerythritol. Esters can also be monoestersof mono-carboxylic acids and monohydric alcohols.

Natural (or bio-derived) esters refer to materials derived from arenewable biological resource, organism, or entity, distinct frommaterials derived from petroleum or equivalent raw materials. Naturalesters include fatty acid triglycerides, hydrolyzed or partiallyhydrolyzed triglycerides, or transesterified triglyceride esters, suchas fatty acid methyl ester (or FAME). Suitable triglycerides include,but are not limited to, palm oil, soybean oil, sunflower oil, rapeseedoil, olive oil, linseed oil, and related materials. Other sources oftriglycerides include, but are not limited to, algae, animal tallow, andzooplankton. Methods for producing biolubricants from naturaltriglycerides are described in, e.g., United States Patent Publication2011/0009300A1.

In one embodiment, the lubricating composition comprises at least 2 wt %of an ester base fluid. In one embodiment the lubricating composition ofthe invention comprises at least 4 wt % of an ester base fluid, or atleast 7 wt % of an ester base fluid, or even at least 10 wt % of anester base fluid.

Metal Overbased Detergent

Metal overbased detergents, otherwise referred to as overbaseddetergents, metal-containing overbased detergents or superbased salts,are characterized by a metal content in excess of that which would benecessary for neutralization according to the stoichiometry of the metaland the particular acidic organic compound, i.e. the substrate, reactedwith the metal. The overbased detergent may comprise one or more ofnon-sulfur containing phenates, sulfur containing phenates, sulfonates,salicylates, and mixtures thereof.

The amount of excess metal is commonly expressed in terms of substrateto metal ratio. The terminology “metal ratio” is used in the prior artand herein to define the ratio of the total chemical equivalents of themetal in the overbased salt to the chemical equivalents of the metal inthe salt which would be expected to result from the reaction between thehydrocarbyl substituted organic acid; the hydrocarbyl-substituted phenolor mixtures thereof to be overbased, and the basic metal compoundaccording to the known chemical reactivity and the stoichiometry of thetwo reactants. Thus, in a normal or neutral salt (i.e. soap) the metalratio is one and, in an overbased salt, the metal ratio is greater thanone, especially greater than 1.3. The overbased detergent of theinvention may have a metal ratio of 5 to 30, or a metal ratio of 7 to22, or a metal ratio of at least 11.

The metal-containing detergent may also include “hybrid” detergentsformed with mixed surfactant systems including phenate and/or sulfonatecomponents, e.g. phenate-salicylates, sulfonate-phenates,sulfonate-salicylates, sulfonates-phenates-salicylates, as described,for example, in U.S. Pat. Nos. 6,429,178; 6,429,179; 6,153,565; and6,281,179. Where, for example, a hybrid sulfonate/phenate detergent isemployed, the hybrid detergent would be considered equivalent to amountsof distinct phenate and sulfonate detergents introducing like amounts ofphenate and sulfonate soaps, respectively. Overbased phenates andsalicylates typically have a total base number of 180 to 450 TBN.Overbased sulfonates typically have a total base number of 250 to 600,or 300 to 500. Overbased detergents are known in the art.

Alkylphenols are often used as constituents in and/or building blocksfor overbased detergents. Alkylphenols may be used to prepare phenate,salicylate, salixarate, or saligenin detergents or mixtures thereof.Suitable alkylphenols may include para-substituted hydrocarbyl phenols.The hydrocarbyl group may be linear or branched aliphatic groups of 1 to60 carbon atoms, 8 to 40 carbon atoms, 10 to 24 carbon atoms, 12 to 20carbon atoms, or 16 to 24 carbon atoms. In one embodiment, thealkylphenol overbased detergent is prepared from an alkylphenol ormixture thereof that is free of or substantially free of (i.e. containsless than 0.1 weight percent) p-dodecylphenol. In one embodiment, thelubricating composition of the invention contains less than 0.3 weightpercent of alkylphenol, less than 0.1 weight percent of alkylphenol, orless than 0.05 weight percent of alkylphenol.

The overbased metal-containing detergent may be alkali metal or alkalineearth metal salts. In one embodiment, the overbased detergent may besodium salts, calcium salts, magnesium salts, or mixtures thereof of thephenates, sulfur-containing phenates, sulfonates, salixarates andsalicylates. In one embodiment, the overbased detergent is a calciumdetergent, a magnesium detergent or mixtures thereof. In one embodiment,the overbased calcium detergent may be present in an amount to deliverat least 500 ppm calcium by weight and no more than 3000 ppm calcium byweight, or at least 1000 ppm calcium by weight, or at least 2000 ppmcalcium by weight, or no more than 2500 ppm calcium by weight to thelubricating composition. In one embodiment, the overbased detergent maybe present in an amount to deliver no more than 500 ppm by weight ofmagnesium to the lubricating composition, or no more than 330 ppm byweight, or no more than 125 ppm by weight, or no more than 45 ppm byweight. In one embodiment, the lubricating composition is essentiallyfree of (i.e. contains less than 10 ppm) magnesium resulting from theoverbased detergent. In one embodiment, the overbased detergent may bepresent in an amount to deliver at least 200 ppm by weight of magnesium,or at least 450 ppm by weight magnesium, or at least 700 ppm by weightmagnesium to the lubricating composition. In one embodiment, bothcalcium and magnesium containing detergents may be present in thelubricating composition. Calcium and magnesium detergents may be presentsuch that the weight ratio of calcium to magnesium is 10:1 to 1:10, or8:3 to 4:5, or 1:1 to 1:3. In one embodiment, the overbased detergent isfree of or substantially free of sodium.

In one embodiment, the sulfonate detergent may be predominantly a linearalkylbenzene sulfonate detergent having a metal ratio of at least 8 asis described in paragraphs [0026] to [0037] of US Patent Publication2005/065045 (and granted as U.S. Pat. No. 7,407,919). The linearalkylbenzene sulfonate detergent may be particularly useful forassisting in improving fuel economy. The linear alkyl group may beattached to the benzene ring anywhere along the linear chain of thealkyl group, but often in the 2, 3 or 4 position of the linear chain,and in some instances, predominantly in the 2 position, resulting in thelinear alkylbenzene sulfonate detergent.

Salicylate detergents and overbased salicylate detergents may beprepared in at least two different manners. Carbonylation (also referredto as carboxylation) of a p-alkylphenol is described in many referencesincluding U.S. Pat. No. 8,399,388. Carbonylation may be followed byoverbasing to form overbased salicylate detergent. Suitablep-alkylphenols include those with linear and/or branched hydrocarbylgroups of 1 to 60 carbon atoms. Salicylate detergents may also beprepared by alkylation of salicylic acid, followed by overbasing, asdescribed in U.S. Pat. No. 7,009,072. Salicylate detergents prepared inthis manner, may be prepared from linear and/or branched alkylatingagents (usually 1-olefins) containing 6 to 50 carbon atoms, 10 to 30carbon atoms, or 14 to 24 carbon atoms. In one embodiment, the overbaseddetergent of the invention is a salicylate detergent. In one embodiment,the salicylate detergent of the invention is free of unreactedp-alkylphenol (i.e. contains less than 0.1 weight percent). In oneembodiment, the salicylate detergent of the invention is prepared byalkylation of salicylic acid.

The overbased detergent may be present at 0.2 wt % to 15 wt %, or 0.3 wt% to 10 wt %, or 0.3 wt % to 8 wt %, or 0.4 wt % to 3 wt %. For example,in a heavy duty diesel engine, the detergent may be present at 2 wt % to3 wt % of the lubricating composition. For a passenger car engine, thedetergent may be present at 0.2 wt % to 1 wt % of the lubricatingcomposition.

Metal-containing detergents contribute sulfated ash to a lubricatingcomposition. Sulfated ash may be determined by ASTM D874. In oneembodiment, the lubricating composition of the invention comprises ametal-containing detergent in an amount to deliver at least 0.4 weightpercent sulfated ash to the total composition. In another embodiment,the metal-containing detergent is present in an amount to deliver atleast 0.6 weight percent sulfated ash, or at least 0.75 weight percentsulfated ash, or even at least 0.9 weight percent sulfated ash to thelubricating composition. In one embodiment, the metal-containingoverbased detergent is present in an amount to deliver 0.1 weightpercent to 0.8 weight percent sulfated ash to the lubricatingcomposition.

In addition to ash and TBN, overbased detergents contribute detergentsoap, also referred to as neutral detergent salt, to the lubricatingcomposition. Soap, being a metal salt of the substrate, may act as asurfactant in the lubricating composition. In one embodiment, thelubricating composition comprises 0.05 weight percent to 1.5 weightpercent detergent soap, or 0.1 weight percent to 0.9 weight percentdetergent soap. In one embodiment, the lubricating composition containsno more than 0.5 weight percent detergent soap. The overbased detergentmay have a weight ratio of ash:soap of 5:1 to 1:2.3, or 3.5:1 to 1:2, or2.9:1 to 1:1:7.

Other Performance Additives

The compositions of the invention may optionally comprise one or moreadditional performance additives. These additional performance additivesmay include one or more metal deactivators, viscosity modifiers,antioxidants, friction modifiers, antiwear agents, corrosion inhibitors,dispersants, dispersant viscosity modifiers, extreme pressure agents,antioxidants (other than those of the invention), foam inhibitors,demulsifiers, pour point depressants, seal swelling agents, and anycombination or mixture thereof. Typically, fully-formulated lubricatingoil will contain one or more of these performance additives, and often apackage of multiple performance additives

In one embodiment, the invention provides a lubricating compositionfurther comprising a dispersant, an antiwear agent, a dispersantviscosity modifier, a friction modifier, a viscosity modifier, anantioxidant, a detergent (different from that of the invention) or acombination thereof, where each of the additives listed may be a mixtureof two or more of that type of additive. In one embodiment, theinvention provides a lubricating composition further comprising apolyisobutylene succinimide dispersant, an antiwear agent, a dispersantviscosity modifier, a friction modifier, a viscosity modifier (typicallyan olefin copolymer such as an ethylene-propylene copolymer), anantioxidant (including phenolic and aminic antioxidants), an overbaseddetergent (including overbased sulfonates and phenates), or acombination thereof, where each of the additives listed may be a mixtureof two or more of that type of additive.

In one embodiment, the invention provides a lubricating compositionwhich further comprises ashless antioxidant. Ashless antioxidants maycomprise one or more of arylamines, diarylamines, alkylated arylamines,alkylated diaryl amines, phenols, hindered phenols, sulfurized olefins,or mixtures thereof. In one embodiment the lubricating compositionincludes an antioxidant, or mixtures thereof. The antioxidant may bepresent at 0 wt % to 15 wt %, or 0.1 wt % to 10 wt %, or 0.5 wt % to 5wt %, or 0.5 wt % to 3 wt %, or 0.3 wt % to 1.5 wt % of the lubricatingcomposition.

The diarylamine or alkylated diarylamine may be a phenyl-α-naphthylamine(PANA), an alkylated diphenylamine, or an alkylated phenylnapthylamine,or mixtures thereof. The alkylated diphenylamine may includedi-nonylated diphenylamine, nonyl diphenylamine, octyl diphenylamine,di-octylated diphenylamine, di-decylated diphenylamine, decyldiphenylamine and mixtures thereof. In one embodiment, the diphenylaminemay include nonyl diphenylamine, dinonyl diphenylamine, octyldiphenylamine, dioctyl diphenylamine, or mixtures thereof. In oneembodiment the alkylated diphenylamine may include nonyl diphenylamine,or dinonyl diphenylamine. The alkylated diarylamine may include octyl,di-octyl, nonyl, di-nonyl, decyl or di-decyl phenylnapthylamines.

The diarylamine antioxidant of the invention may be present on a weightbasis of this lubrication composition at 0.1% to 10%, 0.35% to 5%, oreven 0.5% to 2%.

The phenolic antioxidant may be a simple alkyl phenol, a hinderedphenol, or coupled phenolic compounds.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupmay be further substituted with a hydrocarbyl group (typically linear orbranched alkyl) and/or a bridging group linking to a second aromaticgroup. Examples of suitable hindered phenol antioxidants include2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol,4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol or4-butyl-2,6-di-tert-butylphenol, 4-dodecyl-2,6-di-tert-butylphenol, orbutyl 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate. In one embodiment,the hindered phenol antioxidant may be an ester and may include, e.g.,Irganox™ L-135 from Ciba.

Coupled phenols often contain two alkylphenols coupled with alkylenegroups to form bisphenol compounds. Examples of suitable coupled phenolcompounds include 4,4′-methylene bis-(2,6-di-tert-butyl phenol),4-methyl-2,6-di-tert-butylphenol, 2,2′-bis-(6-t-butyl-4-heptylphenol);4,4′-bis(2,6-di-t-butyl phenol),2,2′-methylenebis(4-methyl-6-t-butylphenol), and 2,2′-methylenebis(4-ethyl-6-t-butylphenol).

Phenols of the invention also include polyhydric aromatic compounds andtheir derivatives. Examples of suitable polyhydric aromatic compoundsinclude esters and amides of gallic acid, 2,5-dihydroxybenzoic acid,2,6-dihydroxybenzoic acid, 1,4-dihydroxy-2-naphthoic acid,3,5-dihydroxynaphthoic acid, 3,7-dihydroxy naphthoic acid, and mixturesthereof.

In one embodiment, the phenolic antioxidant comprises a hindered phenol.In another embodiment the hindered phenol is derived from2,6-ditertbutyl phenol.

In one embodiment the lubricating composition of the invention comprisesa phenolic antioxidant in a range of 0.01 wt % to 5 wt %, or 0.1 wt % to4 wt %, or 0.2 wt % to 3 wt %, or 0.5 wt % to 2 wt % of the lubricatingcomposition.

Sulfurized olefins are well known commercial materials, and those whichare substantially nitrogen-free, that is, not containing nitrogenfunctionality, are readily available. The olefinic compounds which maybe sulfurized are diverse in nature. They contain at least one olefinicdouble bond, which is defined as a non-aromatic double bond; that is,one connecting two aliphatic carbon atoms. These materials generallyhave sulfide linkages having 1 to 10 sulfur atoms, for instance, 1 to 4,or 1 or 2.

Ashless antioxidants may be used separately or in combination. In oneembodiment of the invention, two or more different antioxidants are usedin combination, such that there is at least 0.1 weight percent of eachof the at least two antioxidants and wherein the combined amount of theashless antioxidants is 0.5 to 5 weight percent. In one embodiment,there may be at least 0.25 to 3 weight percent of each ashlessantioxidant.

In one embodiment, the invention provides a lubricating compositionfurther comprising a molybdenum compound. The molybdenum compound may beselected from the group consisting of molybdenumdialkyldithiophosphates, molybdenum dithiocarbamates, amine salts ofmolybdenum compounds, and mixtures thereof. The molybdenum compound mayprovide the lubricating composition with 0 to 1000 ppm, or 5 to 1000ppm, or 10 to 750 ppm, or 5 ppm to 300 ppm, or 20 ppm to 250 ppm ofmolybdenum.

Suitable dispersants for use in the compositions of the presentinvention include succinimide dispersants. In one embodiment, thedispersant may be present as a single dispersant. In one embodiment, thedispersant may be present as a mixture of two or three differentdispersants, wherein at least one may be a succinimide dispersant.

The succinimide dispersant may be a derivative of an aliphaticpolyamine, or mixtures thereof. The aliphatic polyamine may be aliphaticpolyamine such as an ethylenepolyamine, a propylenepolyamine, abutylenepolyamine, or mixtures thereof. In one embodiment, the aliphaticpolyamine may be ethylenepolyamine. In one embodiment, the aliphaticpolyamine may be selected from the group consisting of ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine, polyamine still bottoms, and mixtures thereof.

The dispersant may be a N-substituted long chain alkenyl succinimide.Examples of N-substituted long chain alkenyl succinimide includepolyisobutylene succinimide. Typically the polyisobutylene from whichpolyisobutylene succinic anhydride is derived has a number averagemolecular weight of 350 to 5000, or 550 to 3000 or 750 to 2500.Succinimide dispersants and their preparation are disclosed, forinstance in U.S. Pat. Nos. 3,172,892, 3,219,666, 3,316,177, 3,340,281,3,351,552, 3,381,022, 3,433,744, 3,444,170, 3,467,668, 3,501,405,3,542,680, 3,576,743, 3,632,511, 4,234,435, Re 26,433, and 6,165,235,7,238,650 and EP Patent 0 355 895B1.

The dispersant may also be post-treated by conventional methods by areaction with any of a variety of agents. Among these are boroncompounds, urea, thiourea, dimercaptothiadiazoles, carbon disulfide,aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinicanhydrides, maleic anhydride, nitriles, epoxides, and phosphoruscompounds.

The dispersant may be present at 0.01 wt % to 20 wt %, or 0.1 wt % to 15wt %, or 0.1 wt % to 10 wt %, or 1 wt % to 6 wt % of the lubricatingcomposition.

In one embodiment, the lubricating composition of the invention furthercomprises a dispersant viscosity modifier. The dispersant viscositymodifier may be present at 0 wt % to 5 wt %, or 0 wt % to 4 wt %, or0.05 wt % to 2 wt % of the lubricating composition.

Suitable dispersant viscosity modifiers include functionalizedpolyolefins, for example, ethylene-propylene copolymers that have beenfunctionalized with an acylating agent such as maleic anhydride and anamine; polymethacrylates functionalized with an amine, or esterifiedstyrene-maleic anhydride copolymers reacted with an amine. More detaileddescription of dispersant viscosity modifiers are disclosed inInternational Publication WO2006/015130 or U.S. Pat. Nos. 4,863,623;6,107,257; 6,107,258; and 6,117,825. In one embodiment, the dispersantviscosity modifier may include those described in U.S. Pat. No.4,863,623 (see column 2, line 15 to column 3, line 52) or inInternational Publication WO2006/015130 (see page 2, paragraph [0008]and preparative examples are described at paragraphs [0065] to [0073]).

In one embodiment, the invention provides a lubricating compositionwhich further includes a phosphorus-containing antiwear agent.Typically, the phosphorus-containing antiwear agent may be a zincdialkyldithiophosphate. Zinc dialkyldithiophosphates are known in theart. The antiwear agent may be present at 0 wt % to 3 wt %, or 0.1 wt %to 1.5 wt %, or 0.5 wt % to 0.9 wt % of the lubricating composition.

In one embodiment, the invention provides a lubricating compositionfurther comprising a friction modifier. Examples of friction modifiersinclude long chain fatty acid derivatives of amines, fatty esters, orepoxides; fatty imidazolines such as condensation products of carboxylicacids and polyalkylene-polyamines; amine salts of alkylphosphoric acids;fatty alkyl tartrates; fatty alkyl tartrimides; or fatty alkyltartramides. The term fatty, as used herein, can mean having a C8-22linear alkyl group.

Friction modifiers may also encompass materials such as sulfurized fattycompounds and olefins, molybdenum dialkyldithiophosphates, molybdenumdithiocarbamates, sunflower oil or monoester of a polyol and analiphatic carboxylic acid.

In one embodiment the friction modifier may be selected from the groupconsisting of long chain fatty acid derivatives of amines, long chainfatty esters, or long chain fatty epoxides; fatty imidazolines; aminesalts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyltartrimides; and fatty alkyl tartramides. The friction modifier may bepresent at 0 wt % to 6 wt %, or 0.05 wt % to 4 wt %, or 0.1 wt % to 2 wt% of the lubricating composition.

In one embodiment, the friction modifier may be a long chain fatty acidester. In another embodiment the long chain fatty acid ester may be amono-ester or a diester or a mixture thereof, and in another embodiment,the long chain fatty acid ester may be a triglyceride.

Other performance additives such as corrosion inhibitors include thosedescribed in paragraphs 5 to 8 of U.S. application Ser. No. 05/038,319,published as WO2006/047486, octyl octanamide, condensation products ofdodecenyl succinic acid or anhydride and a fatty acid such as oleic acidwith a polyamine. In one embodiment, the corrosion inhibitors includethe Synalox® (a registered trademark of The Dow Chemical Company)corrosion inhibitor. The Synalox® corrosion inhibitor may be ahomopolymer or copolymer of propylene oxide. The Synalox® corrosioninhibitor is described in more detail in a product brochure with FormNo. 118-01453-0702 AMS, published by The Dow Chemical Company. Theproduct brochure is entitled “SYNALOX Lubricants, High-PerformancePolyglycols for Demanding Applications.”

The lubricating composition may further include metal deactivators,including derivatives of benzotriazoles (typically tolyltriazole),dimercaptothiadiazole derivatives, 1,2,4-triazoles, benzimidazoles,2-alkyldithiobenzimidazoles, or 2-alkyldithiobenzothiazoles; foaminhibitors, including copolymers of ethyl acrylate and2-ethylhexylacrylate and copolymers of ethyl acrylate and2-ethylhexylacrylate and vinyl acetate; demulsifiers including trialkylphosphates, polyethylene glycols, polyethylene oxides, polypropyleneoxides and (ethylene oxide-propylene oxide) polymers; and pour pointdepressants, including esters of maleic anhydride-styrene,polymethacrylates, polyacrylates or polyacrylamides.

Pour point depressants that may be useful in the compositions of theinvention further include polyalphaolefins, esters of maleicanhydride-styrene, poly(meth)acrylates, polyacrylates orpolyacrylamides.

In different embodiments the lubricating composition may have acomposition as described in the following table:

Embodiments (wt %) Additive A B C Antioxidant of Invention 0.05 to 1 0.2to 3  0.5 to 2 Dispersant 0.05 to 12 0.75 to 8  0.5 to 6 DispersantViscosity Modifier 0 or 0 or 0.05 to 2  0.05 to 5 0.05 to 4 OverbasedDetergent 0 or 0.1 to 10 0.2 to 8 0.05 to 15 Additional Antioxidant 0 or0.1 to 10 0.5 to 5 0.05 to 15 Antiwear Agent 0 or 0.1 to 10 0.3 to 50.05 to 15 Friction Modifier 0 or 0.05 to 4  0.1 to 2 0.05 to 6Viscosity Modifier 0 or 0.5 to 8    1 to 6 0.05 to 10 Any OtherPerformance Additive 0 or 0 or 0 or 0.05 to 10 0.05 to 8 0.05 to 6 Oilof Lubricating Viscosity Balance to Balance to Balance to 100% 100% 100%

The present invention provides a surprising ability to prevent damage toan engine in operation due to pre-ignition events resulting from directgasoline injection into the combustion chamber. This is accomplishedwhile maintaining fuel economy performance, low sulfated ash levels,improved deposit control, and other limitations, required byincreasingly stringent government regulations.

INDUSTRIAL APPLICATION

As described above, the invention provides for a method of lubricatingan internal combustion engine comprising supplying to the internalcombustion engine a lubricating composition as disclosed herein.Generally, the lubricant is added to the lubricating system of theinternal combustion engine, which then delivers the lubricatingcomposition to the critical parts of the engine, during its operation,that require lubrication

The lubricating compositions described above may be utilized in aninternal combustion engine. The engine components may have a surface ofsteel or aluminum (typically a surface of steel), and may also be coatedfor example with a diamondlike carbon (DLC) coating.

An aluminum surface may be comprised of an aluminum alloy that may be aeutectic or hyper-eutectic aluminum alloy (such as those derived fromaluminum silicates, aluminum oxides, or other ceramic materials). Thealuminum surface may be present on a cylinder bore, cylinder block, orpiston ring having an aluminum alloy, or aluminum composite.

The internal combustion engine may be fitted with an emission controlsystem or a turbocharger. Examples of the emission control systeminclude diesel particulate filters (DPF), or systems employing selectivecatalytic reduction (SCR).

The internal combustion engine of the present invention is distinct froma gas turbine. In an internal combustion engine, individual combustionevents translate from a linear reciprocating force into a rotationaltorque through the rod and crankshaft. In contrast, in a gas turbine(which may also be referred to as a jet engine) a continuous combustionprocess generates a rotational torque continuously without translation,and can also develop thrust at the exhaust outlet. These differences inoperation conditions of a gas turbine and internal combustion engineresult in different operating environments and stresses.

The lubricant composition for an internal combustion engine may besuitable for any engine lubricant irrespective of the sulfur, phosphorusor sulfated ash (ASTM D-874) content. The sulfur content of the engineoil lubricant may be 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % orless, or 0.3 wt % or less. In one embodiment, the sulfur content may bein the range of 0.001 wt % to 0.5 wt %, or 0.01 wt % to 0.3 wt %. Thephosphorus content may be 0.2 wt % or less, or 0.12 wt % or less, or 0.1wt % or less, or 0.085 wt % or less, or 0.08 wt % or less, or even 0.06wt % or less, 0.055 wt % or less, or 0.05 wt % or less. In oneembodiment the phosphorus content may be 100 ppm to 1000 ppm, or 200 ppmto 600 ppm. The total sulfated ash content may be 2 wt % or less, or 1.5wt % or less, or 1.1 wt % or less, or 1 wt % or less, or 0.8 wt % orless, or 0.5 wt % or less, or 0.4 wt % or less. In one embodiment, thesulfated ash content may be 0.05 wt % to 0.9 wt %, or 0.1 wt % to 0.2 wt% or to 0.45 wt %.

In one embodiment, the lubricating composition may be an engine oil,wherein the lubricating composition may be characterized as having atleast one of (i) a sulfur content of 0.5 wt % or less, (ii) a phosphoruscontent of 0.1 wt % or less, (iii) a sulfated ash content of 1.5 wt % orless, or combinations thereof.

EXAMPLES

The invention will be further illustrated by the following examples,which set forth particularly advantageous embodiments. While theexamples are provided to illustrate the invention, they are not intendedto limit it.

Lubricating Compositions

A series of 5W-20 engine lubricants in Group II base oil of lubricatingviscosity are prepared containing the additives described above as wellas conventional additives including polymeric viscosity modifier,ashless succinimide dispersant, overbased detergents, antioxidants(combination of phenolic ester and diarylamine), zincdialkyldithiophosphate (ZDDP), as well as other performance additives asfollows (Table 1). The phosphorus, sulfur and ash contents of each ofthe examples are also presented in the table in part to show that eachexample has a similar amount of these materials and so provide a propercomparison between the comparative and invention examples.

TABLE 1 Lubricating Oil Composition Formulations¹ COMP EX1 INV EX2 INVEX3 INV EX4 INV EX5 INV EX6 Group III Base Oil Balance to = 100% CaSulfonate 1² 0 0.26 1.13 0 0.76 0.51 Ca Sulfonate 2³ 0 0.12 0 0.06 0.35Ca Sulfonate 3⁴ 1.0 0 0 0 0 0 Ca Phenate⁵ 0 0 0 1.4 0 0 Na Sulfonate⁶0.18 0.09 0 0 0.26 0.18 Mg Sulfonate⁷ 0 0 0 0 0 0 Ashless Antioxidant⁸1.4 0.725 1.4 2.0 2.18 4.0 Dispersant⁹ 2.5 1.2 2.0 4.6 3.6 2.4 ZDDP 0.760.4 0.7 0.45 1.1 0.76 VI Improver 1.0 1.0 2.1 1.1 1.0 0.55 AdditionalAdditives¹⁰ 1.0 0.85 1.4 0.58 2.1 2.0 % Phosphorus 0.076 0.038 0.0600.046 0.11 0.076 % Calcium 0.168 0.084 0.234 0.123 0.251 0.168 % Sodium0.049 0.024 0 0 0.073 0.049 % Molybdenum (ppm) 0 46 0 0 140 90 TB N 10.83.84 7.75 6.1 11.5 10.8 % Ash 0.9 0.44 0.9 0.50 1.31 0.88 ¹All amountsshown above are in weight percent and are on an oil-free basis unlessotherwise noted. ²Ca Sulfonate 1: Overbased calcium sulfonate with oilfree TBN of 520; metal ratio of 10 ³Ca Sulfonate 2: Overbased calciumsulfonate with oil free TBN of 690; metal ratio of 18 ⁴Ca Sulfonate 3:Overbased calcium sulfonate with oil free TBN of 160; metal ratio of 2.8⁵Ca Phenate: “Neutral” calcium phenate with oil free TBN of 200; metalratio of 1.2 ⁶Na Sulfonate: Overbased Na sulfonate with oil free TBN of650 ⁷Mg Sulfonate: Overbased Mg sulfonate with oil free TBN of 600⁸Combination of alkylated diarylamine and hindered phenol antioxidants⁹Dispersant: PIBsuccinimide prepared from 2000 Mn PIB ¹⁰The AdditionalAdditives used in the examples include friction modifiers, pourpointdepressants, anti-foam agents, corrosion inhibitors, and includes someamount of diluent oil

TABLE 2 Lubricating Oil Composition Formulations (5W-30) EX7 EX8 EX9EX10 EX11 EX12 EX13 Group III Base Oil Balance to = 100% Ca Sulfonate²2.78 1.12 1.12 0.95 2.62 0.29 2.78 Mg Sulfonate³ 0 0 0 0 0 2.92 0 NaSulfonate 0 0 0 0.15 0 0 0 Ca Phenate⁴ 0 0 0 0 0.58 0 0 Dispersant 2.722.72 2.72 2.72 2.0 2.0 2.0 Ashless Antioxidant⁵ 1.6 1.6 1.6 1.6 0.850.85 0.85 ZDDP 0.32 0.32 0.77 0.77 0.32 0.32 0.32 VI Improver 0.6 0.60.6 0.6 0.6 0.4 0.6 Additional Additives⁶ 0.9 0.9 0.9 0.9 0.36 0.36 0.36% Calcium 0.75 0.25 0.25 0.21 0.72 0.064 0.71 % Magnesium 0 0 0 0 0 0.420 % Sodium 0 0 0 0.045 0 0 0 Sulfated Ash 2.52 0.92 0.99 0.99 2.52 2.262.52 % Phosphorus 0.03 0.03 0.076 0.076 0.03 0.03 0.03 ¹All amountsshown above are in weight percent and are on an oil-free basis unlessotherwise noted less otherwise noted. ²Ca Sulfonate is one or moreoverbased calcium alkylbenzene sulfonic acid with TBN at least 300 andmetal ratio at least 10 ³Overbased magnesium sulfonate with TBN of ~600⁴Sulfur coupled phenate salt of calcium with TBN of ~200 ⁵Ashlessantioxidant - mixture of nonylated and dinonylatyd diphenylamine,hindered phenol ester and sulfurized olefin ⁶The Additional Additivesused in the examples include friction modifiers, pourpoint depressants,anti-foam agents, corrosion inhibitors, and includes some amount ofdiluent oil.Testing

Low Speed Pre-ignition events are measured in two engines, a Ford 2.0 LEcoboost engine and a GM 2.0 L Ecotec. Both of these engines areturbocharged gasoline direct injection (GDI) engines. The Ford Ecoboostengine is operated in two stages. In the first stage, the engine isoperated at 1500 rpm and 14.4 bar brake mean effective pressure (BMEP).During the second stage, the engine is operated at 1750 rpm and 17.0 barBMEP. The engine is run for 25,000 combustion cycles in each stage, andLSPI events are counted.

The GM Ecotec engine is operated at 2000 rpm and 22.0 bar BMEP with anoil sump temperature of 100° C. The test consists of nine phases of15,000 combustion cycles with each phase separated by an idle period.Thus, combustion events are counted over 135,000 combustion cycles.

LSPI events are determined by monitoring peak cylinder pressure (PP) andmass fraction burn (MFB) of the fuel charge in the cylinder. When bothcriteria are met, it is determined that an LSPI event has occurred. Thethreshold for peak cylinder pressure is typically 9,000 to 10,000 kPa.The threshold for MFB is typically such that at least 2% of the fuelcharge is burned late, i.e. 5.5 degrees After Top Dead Center (ATDC).LSPI events can be reported as events per 100,000 combustion cycles,events per cycle, and/or combustion cycles per event.

TABLE 4 GM Ecotec LSPI Testing EX7 EX8 EX9 EX10 EX11 EX12 EX13 PP Events26 17 11 6 33 4 44 MFB Events 29 18 12 7 36 3 46 Total Events 26 17 11 632 3 43 Total Cycles 135000 135000 135000 135000 135000 135000 135000Ave. PP 18440 20670 20520 13300 18980 17370 18860 Events per 100,00019.2 12.6 8.1 4.4 23.7 2.2 31.8 cycles Cycles per event 5192 7941 1227322500 4219 45000 3140

The data indicates that a reduction in total detergent ash below 1weight percent results in a reduction in LSPI events. Partialreplacement of calcium detergent with magnesium and/or sodium detergentalso provided an observed reduction in LSPI events. In addition, partialreplacement of sulfonate detergent with phenate-based detergent resultedin a reduction in observable LSPI events.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. The productsformed thereby, including the products formed upon employing lubricantcomposition of the present invention in its intended use, may not besusceptible of easy description. Nevertheless, all such modificationsand reaction products are included within the scope of the presentinvention; the present invention encompasses lubricant compositionprepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference, as is the priority document and all related applications, ifany, which this application claims the benefit of. Except in theExamples, or where otherwise explicitly indicated, all numericalquantities in this description specifying amounts of materials, reactionconditions, molecular weights, number of carbon atoms, and the like, areto be understood as modified by the word “about.” Unless otherwiseindicated, each chemical or composition referred to herein should beinterpreted as being a commercial grade material which may contain theisomers, by-products, derivatives, and other such materials which arenormally understood to be present in the commercial grade. However, theamount of each chemical component is presented exclusive of any solventor diluent oil, which may be customarily present in the commercialmaterial, unless otherwise indicated. It is to be understood that theupper and lower amount, range, and ratio limits set forth herein may beindependently combined. Similarly, the ranges and amounts for eachelement of the invention may be used together with ranges or amounts forany of the other elements.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl oralkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, andaromatic-, aliphatic-, and alicyclic-substituted aromatic substituents,as well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (e.g., two substituents together form aring); (ii) substituted hydrocarbon substituents, that is, substituentscontaining non-hydrocarbon groups which, in the context of thisinvention, do not alter the predominantly hydrocarbon nature of thesubstituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy,mercapto, alkylmercapto, nitro, nitroso, and sulphoxy); (iii) heterosubstituents, that is, substituents which, while having a predominantlyhydrocarbon character, in the context of this invention, contain otherthan carbon in a ring or chain otherwise composed of carbon atoms.

Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituentsas pyridyl, furyl, thienyl and imidazolyl. In general, no more than two,preferably no more than one, non-hydrocarbon substituent will be presentfor every ten carbon atoms in the hydrocarbyl group; typically, therewill be no non-hydrocarbon substituents in the hydrocarbyl group.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims

What is claimed:
 1. A method for reducing low speed pre-ignition eventsin a spark-ignited direct injection internal combustion engine whereinthe engine is equipped with a turbocharger and is operated under a loadwith a brake mean effective pressure (BMEP) of greater than or equal to12 bars at speeds less than or equal to 3,000 rpm, comprising supplyingto the engine a lubricant composition comprising: (a) a base oil oflubricating viscosity; (b) a magnesium sulfonate overbased detergent inan amount to provide at least 500 ppm magnesium from the magnesiumsulfonate overbased detergent to the lubricating composition; (c) acalcium sulfonate overbased detergent in an amount to provide at least1,000 ppm of calcium from the calcium sulfonate overbased detergent tothe lubricating composition; (d) 0.5 to 0.9 wt. % of a zincdialkyldithiophosphate anti-wear additive; and (e) 0.5 to 15 weightpercent of one or more additional additives; wherein the magnesiumsulfonate overbased detergent and the calcium sulfonate overbaseddetergent collectively contribute up to about 0.8 weight percent ofsulfated ash to the lubricating composition and wherein the lubricatingcomposition has a phosphorus content of 0.12 wt. % or less and totalsulfated ash of 1.1% or less.
 2. The method of claim 1, wherein theengine is fueled with a liquid hydrocarbon fuel, a liquid nonhydrocarbonfuel, or mixtures thereof.
 3. The method of claim 2, wherein the engineis fueled by natural gas, liquefied petroleum gas (LPG), compressednatural gas (CNG), or mixtures thereof.
 4. The method of claim 1,wherein the one or more additional additives is selected from an ashlessdispersant, an ashless antioxidant, a friction modifier, and a polymericviscosity modifier.
 5. The method of claim 1, wherein the magnesiumoverbased detergent has a metal ratio of 5 to
 30. 6. The method of claim1, wherein the magnesium overbased detergent is present in an amountfrom 0.2 to 8 weight percent of the lubricant composition.
 7. The methodof claim 1, wherein the one or more additional additives is apolyalkenyl succinimide dispersant in an amount from 0.5 to 4 weight %of the lubricating composition.
 8. The method of claim 1, wherein thebase oil comprises at least 50 weight % of a Group II base oil, a GroupIII base oil, or mixtures thereof.
 9. The method of claim 1, whereinthere is a reduction in the number of LSPI events of at least 10percent.
 10. The method of claim 1, wherein the low speed pre-ignitionevents are reduced to less than 20 LSPI events per 100,000 combustionevents.